714 GENERAL TECHNIQUES FOR CLASSES OF PLANTS 



except the youngest stages. Individual cone scales are best cut 

 back to the ovule, when the tips become hard. In older stages, 

 remove the ovules from the scale and trim them as far as possible. 

 LuTZ {Stain Tech., vi, 1931, p. 123) describes a method for pre- 

 paring thick sections of mature pine cones. Thoroughly air-dry 

 the cone and imbed in paraffin wax of melting point 56° to 58° C. 

 Cooling must be quick and complete. Mark lines of sections on 

 the paraffin and cut section with either a hacksaw or carpenter's 

 handsaw. Dress down the surface with sand-paper and, if 

 required, coat the polished surface with white shellac. 



1406. BucHHOLz's Method for Pinus Embryo {Bot. Gaz., Ixvi, 

 1918, p. 185). Dissect the embryo from living material under 

 a 0-3 grm. molar sugar solution (about 10-3 per cent.). Isolate 

 the gametophyte first and hold it gently with forceps by the 

 broad end and make a cut right round the narrow end with a 

 needle shaped to an arrow-head tip and keenly sharpened. Gently 

 remove this end, and by teasing into the end of the ovule expose 

 the rosette ends of the suspensors, which should be pushed out by 

 the straightening suspensors. By successive segmental cuts the 

 distal portions of the suspensors and the embryo, are exposed, and 

 the whole complex removed. Fix in formol alcohol, and stain in 

 Delafield's haematoxylin, the embryo being handled by means of 

 wide-tipped pipettes. Dehydrate through glycerin and infiltrate 

 with Venetian turpentine or balsam. 



ANGIOSPERM.E 



1407. Pollen Morphology. Wodehouse {Journ. New York Bot. 

 Gard., xxvii, 1926, p. 145) recommends that grains be examined 

 both dry and moist. The latter condition reveals more characters 

 to advantage. Wodehouse {Ann. Bot., xlii, 1928, p. 891) gives 

 methods for preparation of microscopic mounts and {Bull. Torrey 

 Bot. Club, Ix, 1933, p. 417) for catching and counting atmospheric 

 pollen. He recommends an alcohol-water-glycerin combination 

 for temporary preparations, and Brandt's glycerin jelly for per- 

 manent ones. For a stain he uses aqueous methyl blue, since it 

 stains the exine selectively ; it fades in eight to nine months. 

 The procedure is : Take a little pollen on the tip of a scalpel, 

 place on a slide, moisten with a drop of 95 per cent, alcohol and 

 stir with a needle to a paste, which rapidly dries, leaving the pollen 

 lightly stuck to the slide. Wash by flowing alcohol over the pollen 

 and drawing off with filter-paper. When nearly dry add a drop of 

 methyl blue and warm to hasten staining ; draw off excess with 

 filter-paper. Add a little melted glycerin jelly and cover. Allow 

 jelly to set with slide inverted, so that grains may be close to the 

 cover. 



He also details the treatment of herbarium specimens. Moisten 



